Method of bonding aluminum to steel



Oct. 11, 1949. R. s. REYNOLDS 2,484,118

METHOD OF BONDING ALUMINUM T0 STEEL Filed Sept. 22, 1944 ALUMINUM 0R ALUMINUM ALLO Y) Wyzgog BY 04L,

ATTORN EY Patented Get. ii, 1949 METHOD OF BONDING ALUMINUM T STEEL Richard S. Reynolds, Richmond, Va., assignor to Reynolds Metals Company, Richmond, Va., a corporation of Delaware Application September 22, 1944, Serial No. 555,397

2 Claims. (Cl. 29-189) 1 This invention relates to the cladding of steel with aluminum and aluminum alloys, and in the preferred method the steel is encased with aluminum sheet or foil in continuous strip.

aluminum alloy is very difficult.

under heat and pressure.

iron anode plate within the tank, and from time to time increasing the ferric content of the ferrous salt solution to maintain the concentration of the solution such that it has ferric iron approximately 1% of the total iron content thereof.

Upon emerging from the fur- Many methods have been proposed for clad- 5 ding steel with aluminum, as by hot and cold In order to provide a continuous process the rolling, and by dipping the steel, previously steel strip may be led through the tank back cleaned, in molten aluminum. However, there and forth about two vertical sets of supporting are many difiiculties in such processes, particurollers, which rollers may be glass surfaced larly when hard aluminum alloys are sought as provided with any surface not affected by the the cladding material, because the securing of a plating b r the plating hath the Strip satisfactory bond between the steel and the s l d, in its co i uous movement, to a Washing station, followed by a drying station.

My method is characterized by the provision The rate of deposition of the pure electrolytic of an interface between the two metals which iron, the p d Of he tr p through the plating consists of electrodeposited iron, carried by the bath, and the length of travel o the Strip in e steel, the deposit of the iron being sumcient to bath are interrelated factors which determine completely cover the entire surface areas of the the thickness .of the electrolytic iron deposition. steel which are to receive the cladding. Thus, It is y necessary that the deposit he Sufficient a smooth and uniform deposit of pure electrolytic to entirely cover the steel strip with a smooth iron is employed for its bonding action, the iron pos of e ectroly c o a d in y being relatively soft and lending itself to the as s it ll be suffici nt to d p sit a thick ss integral bonding of aluminum cladding and steel 0f for ctiv bonding of a a um m alloy foil or sheet.

The accompanying drawing illustrates dia- Upon the dry 0f e ferrous p d Steel Strip grammatically the layers in the composite body. it will, in conditions of cold rolling. be ready to As an example, steel strip of a desired thickreceive a web of aluminum foil, if one surface is ness, as for example that permitting the strip o e clad, tWO we of Such foil, if bo $111- to be wound into a coil, is run continuously faces of the steel strip are to be clad. By alumithrough a series of tanks, the first containing a num f I a more partieulally T011 0f alumipickling or alkali cleaning bath, employing any num alloys diflicult for the cladding of steel. In of the customary solutions as practiced in the eu of the o al or aluminum oy w bs treatment of metals prior to electroplating. of a gauge thicker than that of foil may be em- Thus, a pickling bath employing 10% hydroployed as the cladding material. As an example, chloric acid solution may be employed. The secin the cold-cladding of the steel strip with its 0nd tank may contain washing elements for surfaces of pure electrolytic iron, the steel strip washing the steel strip, the latter passing to an in its continuous movement from the drying zone, electroplating tank where the pure electrolytic may be led between two spaced rolls of wound iron is deposited upon the steel strip. or coiled aluminum foil or'sheet as the case may Although there are many types of ferrous- -10 be, and the three, 1. e. the steel strip and the two plating solutions, with varying electrolytes and webs of aluminum foil or sheet may be brought operating conditions, which may be employed, between the contact rollers of a rolling mill, I prefer to use the method of making electrowhereby through high pressure the bonding of deposited iron which is the subject of the Whitthe laminated structure is efiected. field and Sheshunofi Patent 2,223,928 of Decem- Ordinarily the bonding will be eflected both her 3, 1940. The said method is desirable beunder heat and pressure. To this end the strip cause it affords economical procedure by which of ferrous coated steel may, in its continuous films or layers of any desired thickness may be movement, be led though a furnace and there deposited upon the steel strip by relatively simple subjected to a suitably high temperature, as for apparatus, the deposit having smooth surfaces example 800-900 F., preferably in a non-oxidizfree of pinholes. Briefly, the method is to circuing atmosphere. late within a single tank-like cell an acid solunace, the hot steel strip may be led to the hot tion of ferrous salt, the solution being subjected rolls between webs of aluminum foil or sheet, for to electrolysis between the steel strip as a bonding under high pressure, customary with the cathode and a suitable anode, such as a cost reduction of aluminum plate into sheet. The

composite structure leaving the hot roll will be reduced in thickness,and it can be further rolled to reduce thickness, coiled for further heat treatment, or cut into sheets for use or further heat treatment.

As an alternative, the steel strip leaving the ferrous plating, washing and drying stations may then receive the aluminum sheet or foil webs fed into surface contact with the electro-deposited surfaces of the steel stripand under substantial roll pressure for a light bond thereto. The com posite structure in its continued movement may then be led through the furnace for heating, followed by hot rolling and treatment as before stated.

In a still applicable method the ferrous plated steel strip carrying the cladding sheets a foil, lightly bonded to the strip by roll pressure, may be loosely coiled by the usual coiling basket devices, and then transferred to the furnace for heating. Thus a stock of aluminum surfaced steel strip coils may be heated and made ready for the hot rolls. v

In the use of the term aluminum herein, I include alloys which are predominantly aluminum.

It will be understood that the method is capable of wide variation in details. For example in the case of some types of aluminum alloy sheets, it may be desirable to first coat the alloy'with commercially pure aluminum, so that the contacting faces in cladding the steel strip will be elec trolytic iron and relatively soft aluminum, both particularly compatible with their carriers and with themselves. The method is obviously applicable to the aluminum cladding of steel plates and cut sheets in addition to strip.

The method also is applicable to the provision of a bonding film consisting of electrolytic iron directly upon sheets of foil of aluminum or aluminum alloys to be employed as cladding material. Either one or both faces of aluminum foil or sheet web may be plated with the electrolytic iron. In the first case the thus plated aluminum or aluminum alloy sheet or foil may be employed as the cladding material, that face carrying electrolytic iron being placed opposite to the steel strip or plate in the bonding operations. In the second case, where both faces of the aluminum or alloy foil or web is coated it will serve as'a bonding medium to be placed intermediate the steel and the aluminum or alloy cladding, as will be understood without further explanation.

As a still further variation a stripped web of electrolytic iron, obtained by the method of the Whitfield and Sheshunofl patent bond referred to may be used as the bonding material between the steel strip and the aluminum or aluminum alloy cladding.

Having described my invention, what I claim and desire to secure by Letters Patent, is as follows:

1. A method of continuously cladding steel strip with aluminum, which consists in feeding steel strip through an electrolytic iron plating bath and depositingrelatively pure electrolytic iron thereon, continuing the movement of the strip through dryingand heating zones, wherein the strip is raised to a temperature of from 800 to 900 F., and bringing aluminum in web form into face association with the steel strip followed by the step of hot rolling under reduction pressure and below the fusing temperature of aluminum.

2. The method of bonding sheet aluminum material to steel which comprises providing the steel with a surface of electro-deposited iron, placing a sheet of aluminum material against the electrodeposited iron surface of the steel, heating said assembly in a non-oxidizing atmosphere to a temperature of from 800 to 900 F., a temperature below the melting point of the sheet aluminum, and applying roller pressure to bond the sheet aluminum material to the steel.

RICHARD S. REYNOLDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,679,308 Jordan July 31, 1928 1,792,377 Jordan Feb. 10, 1931 1,834,203 Cain et al. Dec. 1, 1931 1,984,134 Himmel Dec. 11, 1934 1,997,538 Armstrong Apr. 9, 1935 2,243,979 Reynolds June 3, 1941 2,301,332 Scheller Nov. 10, 1942 2,317,150 Barklie Apr. 27, 1943 

